This blood component separation device has: a centrifuge bowl for separating blood components in blood a plasma bag for storing plasma components a platelet middle bag for storing a high-concentration platelet liquid having a high concentration of platelets and a temporary storage bag, which doubles as a buffy coat bag, for storing a low-concentration platelet liquid having a low concentration of platelets. In this blood component separation device, which, from a second cycle onward, performs control in such a manner as to mix the low-concentration platelet liquid stored in the temporary storage bag with whole blood and feeds said mixture to the centrifuge bowl in the immediately preceding cycle: the amount of the high-concentration platelet liquid collected in the first cycle in which the platelet liquid is collected in the platelet middle bag is compared with the amounts collected in the other cycles, and the amount is set to the lowest value and the amount of the high-concentration platelet liquid collected in the last cycle is compared with the amounts collected in the other cycles, and the amount is set to the highest value.Linvention concerne un dispositif de séparation de composants sanguins, qui comprend : un bol de centrifugation pour la séparation des composants sanguins du sang une poche à plasma pour le stockage des composants plasmatiques une poche centrale à plaquettes pour le stockage dun liquide plaquettaire de concentration élevée contenant une concentration élevée de plaquettes et une poche de stockage temporaire, qui sert également de poche pour couche leucocyto-plaquettaire, pour le stockage dun liquide plaquettaire de concentration faible qui contient une faible concentration de plaquettes. Dans ce dispositif de séparation de composants sanguins qui, à partir dun deuxième cycle, réalise une vérification en mélangeant le liquide plaquettaire de concentration faible contenu dans la poche de stockage temporaire avec du sang total et introduit le
